Constant flow valve



L. F. JASEPH 3,020,891

CONSTANT FLOW VALVE Feb. 13, 1962 Filed June 1, 1959 2 Sheets-Sheet 1 FIG. I

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INVENTOR.

LAWRENCE F. JASEPH Feb. 13, 1962 F. JASEPH 3,020,891

CONSTANT FLOW VALVE Filed June 1, 1959 2 Sheets-$heet 2 FIG. 2

INVEN TOR.

LAWRENCE F. JASEPH 3,020,891 Patented Feb. 13, 1962 3,020,891 CONSTANT FLOW VALVE Lawrence F. Ziaseph, Memphis, Tenn., assignor t Dover Corporation, Washington, 11C. Filed June 1, 1959, Ser. No. 817,358 13 tjlaians. (Cl. 121-46A) The present invention relates to improvements in lowering valves adapted to be used in hydraulic elevator systems for maintaining a constant lowering speed of the elevator car regardless of load variations in the car.

Hydraulic elevators in their modern form are commonly equipped with a jack cylinder and an elevator car supporting plunger reciprocable therein. For raising the elevator car, hydraulic fluid is supplied under pressure to the jack cylinder by means of a pump, and for lowering the car, the hydraulic fluid, which is under pressure due to the supported weight of the plunger, the elevator car, and its load, is allowed to return from the jack cylinder to a reservoir through valve means. It is towards the improvement of said valve means and its relationship to the hydraulic elevator system that the present invention is particularly directed. In the typical hydraulic elevator system of today, said valve means comprises an electrically controlled lowering valve, in which system the speed of descent of the elevator car varies with the load therein, with heavier loads producing faster speeds through an increase in the volumetric rate of fluid flow from the jack cylinder through the lowering valve to the reservoir. In such a system, the speed of downward travel varies nearly as the square root of the load. Since the useful load on a passenger elevator may easily exceed the dead load, the maximum load-speed will exceed the empty-car speed by forty (40%) percent or more. This condition is aggravated in certain higher rise plunger hydraulic elevator installations where the pressure and power required is reduced by partially counter-Weighting the weight of the car and plunger, in which case, the ratio of load borne by the plunger with loaded car to that with empty car is increased, and corresponding lowering speeds may well vary by a factor exceeding two. An accompanying difliculty is encountered in that the distance traveled during stopping varies somewhat with speed, though this is partly overcome by the means disclosed in my Patent No. 2,355,164, issued August 8, 1944.

In years past, the problem mentioned above, of the variation in speeds due to load variations was not quite so pronounced as it is at present, since the car speeds of hydraulic elevator systems were not nearly as fast as those of today. For example, in years past, elevator speeds of fifty (50*) feet per minute were common, whereas, today, speeds of one hundred seventy-five (175) feet per minute are common. Thus, with a no-load speed of fifty (50) feet per minute, a forty (40%) percent increase in speed due to a full load would not be so noticeable since seventy (70) feet per minute would be maximum with a difference of only twenty (20) feet per minute between no-load and full-load speeds. In contrast to this, with a no-load speed of one hundred seventyfive (175) feet per minute, a forty (40%) percent increase in speed due to a full load would be quite objectionable since there would be a two hundred and fortyfive (245) feet per minute maximum and a seventy (70) feet per minute difference.

'In my Patent No. 2,785,660, issued March 19, 1957, one means was disclosed for overcoming the aforementioned difficulties of varying speed and varying stopping distance with variations in car loads, and the present in vention is also intended to overcome these difliculties, but by means improved over that disclosed in said Patent No. 2,785,660, and by means possessing certain advantages thereover, which will become more apparent from a reading of the description of the present invention to follow.

Therefore, one of the objects of the present invention is to provide improved means for controlling the lowering speed of a plunger-type hydraulic elevator or like hydraulic device so that the speed of descent thereof will be substantially constant regardless of normal load variations.

A further object is to provide means for assuring that the distance traveled during the closing of the lowering valve will be uniform as the load varies.

A further object is to provide means for eliminating all leakage from the fluid passage connected to the elevator jack when the latter is stopped.

A further object is to provide a novel arrangement wherein the fluid under pressure from the jack cylinder is introduced through an inlet chamber to theside wall only of the input throttling valve member of the valve assembly of the present invention rather than at an end of the throttling valve member so that the variation of jack pressure in the inlet chamber has no direct effect on the positioning of the input valve member.

A further object is to provide means to compensate for the effect of the variations in the force exerted by the spring that forms part of the positioning means of the input throttling valve member.

A further object is to provide a unitary valve assembly comprising a controlled valve means for selectively varying the effective size of a discharge port, and means for receiving fluid from a source at various pressures and for introducing the fluid to said controlled valve at a constant predetermined value, depending upon the effective size of said port, whereby the volumetric flow through said port is constant for any given effective size of asid port.

A further object is to accomplish the foregoing objects in a simple, economical and highly efiicient manner.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a diagrammatic view of a hydraulic elevator system showing the principal components thereof, including the valve assembly of the present invention.

FIG. 2 is a cross-sectional view of said valve assembly, on a larger scale than FIG. 1 and taken as on a vertical plane through the middle of the valve assembly with certain parts being shown in elevation for purposes of clarity.

FIG. 3 is a fragmentary sectional view taken as on the line III-III of FIG. 2.

FIG. 4 is a fragmentary sectional view on a larger scale than FIGS. 2, and 3, and taken as on a vertical plane through the longitudinal center-line of the input throttling valve of the present invention.

Referring now to the drawings in which the various parts are indicated by numerals, the typical hydraulic elevator system, shown in FIG. 1, with which the valve assembly 11 of the present invention is adapted to be used, includes a jack 13 having a plunger 15 reciprocally mounted in a jack cylinder 17, which is adapted to be buried in the ground or otherwise fixedly supported. An elevator car 18 is supported by plunger 15 adjacent the upper end thereof and is provided with the usual guideways, not shown. At the upper end of cylinder 17 is provided the usual guide 19 attached by bolts or the like to cylinder 17, and suitable resilient packing means indicated as at 21 seals the sliding contact between plunger 15 and guide 19. In addition, a gland 23 adjustably compresses packing means 21 and is secured to guide 19 as by screws or the like. A fluid conduit 25 communicates at one end with the interior of jack cylinder 17 and is branched adjacent the opposite end with one branch or passage 27 extending to valve assembly 11 and the other branch 29 extending to a power unit 31, which includes a hydraulic fluid pump 33, preferably of the constant displacement type; a prime-mover- 35, as an electric motor or the like; and a drive belt. 37. Additionally, the hydraulic system includes a reservoir 39 for hydraulic fluid, a conduit 41 leading from reservoir 39 to pump 33 and a passage 43 leading from. valve assembly 11 t conduit 41. For raising car 18,. hydraulic fluid is supplied under pressure to jack cylinder 17 by means of pump 33. A check valve 45 is provided in the system between branch 29 and pump 33 to prevent reverse flow through the pump. For lowering car 18, the hydraulic fluid, which is under pressure due to its supporting the weight of plunger 15, elevator car 18 and the load therein is allowed to return to reservoir 39 through the valve assembly 11 of the present invention.

From a consideration of the above general description of an elevator system, it will be understood that in prior elevator systems of this type, in which a conventional lowering valve was used in the system in place of valve assembly 11, as the load increased in the elevator car the input pressure to the lowering valve would increase which, in turn, would cause an increase in the volumetric rate of flow of the fluid through the lowering valve, and thus an increase in the lowering speed and stopping distance of the elevator car. The means by which the present invention overcomes these difliculties will be apparent from the following detailed description of valve assembly 11 and its relationship to the elevator system.

Valve assembly 11 includes a hollow valve body 47, including a first partition 49 and a second partition 51 provided in the interior of the valve body to establish an inlet chamber 53, an intermediate chamber 55, and an outlet chamber 57. First partition 49 separates inlet chamber 53 and intermediate chamber 55. Second partition 51 separates intermediate chamber 55 and outlet chamber 57 and also for a portion separates inlet chamber 53 and outlet chamber 57. Inlet chamber 53 and outlet chamber 57 open downwardly through valve body 47 at inlet opening 59 and outlet opening 60, respectively. Chambers 53, 57 are respectively in communication with passages 27, 43 through openings 59, 60 and through openings 61, 62, which latter openings are respectively provided at the ends of passages 27, 43. Valve body .-7 is positioned with opening 59 being in alignment with opening 61 and opening 60 being in alignment with opening 62, as best shown in FIG. 1, and is held in such a position by a flange 63 at the lower end of the valve body, which flange is secured by bolts 65 or the like to a corresponding flange 67 encompassing openings 61, 62. From the foregoing, it will be understood that inlet chamber 53 is substantially in free communication with the interior of jack cylinder 17 whereby the pressure in the inlet chamber is substantially the same as that in the jack cylinder. Also, outlet chamber 57 is in substantially free communication with the reservoir 39 through passage 43 and conduit 41.

First partition 49 is provided with a cylindrical opening 69 therethrough adapted to permit flow of hydraulic fluid from inlet chamber 53 to intermediate chamber 55. A hollow throttling piston member 71, adjacent the inner end 72 thereof, is closely and slidably mounted in cylindrical opening 69; and, adjacent the outer or head end 73 thereof, is closely and slidably mounted in a cylinder 74 provided through the wall of valve body 47 in alignment with opening 69. Piston member 71 spans inlet chamber 53 and the inlet chmabe'r is arranged so that it surrounds the cylindrical side wall 75 of piston member 71. In other words, only the side wall 75 of piston member 71 is exposed to inlet chamber 53 whereby the hydraulic fluid pressure in the inlet chamber is exerted equal ly around the side wall 75 and does not directly influence the position of the piston member in cylindrical opening 69. The cylindrical side wall 75 of piston member 71 at inner end 72 extends into intermediate chamber 55, and is provided with spaced notches 79 so that when the piston member 71 is moved to the right, as viewed in FIG. 2, the notches provide gradually increasing passage area to communicate inlet chamber 53 with intermediate chamber 55 and when the piston member is moved to the left as viewed in this figure, the notches provide gradually decreasing passage area until the piston member reaches its limit in its movement to the left, which limit is shown in FIG. 2 and which substantially closes off opening 69. Thus, the co-action of piston member 71 and opening 69 provides an input throttling valve 80, which is adapted to throttle the fluid flow from inlet chamber 53 to intermediate chamber 55.

A cap 81 is secured to valve body 47 as by bolts 83 and encloses the outer end of cylinder 74 to establish a head chamber 85 which includes the interior of cap 31, the part of cylinder 74 exposed by piston member 71, and the part of the interior of piston member 71 up to an interior transverse bulkhead 87 provided in the piston member intermediate the ends thereof. A plurality of apertures 89 are provided through bulkhead 87 to establish substantially free communication of fluid to either side of the bulkhead so that the fluid pressure in intermediate chamber 55 and head chamber 85 is substantially the same, and for purposes of clarity, this region including head chamber 85 and intermediate chamber 55 is indicated as intermediate pressure region 91.

A stem 93 is integrally attached to bulkhead S7 and extends axially of piston member 71 in a direction away from the head end 73 of the piston member and towards second partition 51. At the end of stem 93 remote from piston member 71 is fixedly attached a piston member 95 that is closely and slidably fitted in a cylinder 97, which is provided in second partition 51 and which is in communication adjacent one end with intermediate chamber 55 and adjacent the opposite end with outlet chamber 57. Piston member 95 and cylinder 97 are smaller in diameter than piston member 71 and opening 69, but are concentric therewith. Cylinder 97 is provided at the end adjacent outlet chmaber 57 with a restriction formed to make a beveled set 99 to mate with a corresponding beveled portion 101 at the end of piston member 95. Beveled seat 99 and beveled portion 101 are ground to fit fluid tight so that when piston member 95 is seated as shown in FIGS. 2 and 4, there is no fluid escape through cylinder 97 from the intermediate pressure region 91. From the foregoing, it will be understood that a unitary valve member 103 is provided, which is adapted to move as a unit and which comprises piston members 71, 95, bulkhead 87, and stem 93.

A compression spring 105 bears against piston member 95 so that the valve member 103 is biased by the spring to the right as viewed in FIG. 2. The end of piston member 95 is preferably provided with a socket 106, which acts as a retainer for the end of spring 105. The opposite end of spring 105 is seated on shims 107 which, in turn, are seated on a cap 109 fastened by bolts 111 or the like to the outer wall of valve body 47 surrounding an aperture 113 provided in valve body 47 and through which spring 105 extends.

From the foregoing, it will be understood that the opposing forces acting on valve member 103 to control the amount of opening or closing of throttling valve 80 are as follows: (1) The opening forces tending to move valve member 103 to the right, as viewed in FIG. 2, to unseat piston member 95 and open throttling valve 80, which openmg forces include spring 105 and pressure in outlet chamber 57 acting on the left end, as viewed in FIG. 2, of piston member 95. (2) The closing forces tending to move valve member 103 to the left, as viewed in FIG. 2, to seat piston member 95 and substantially close throttling valve 80, which closing forces include the force of the fluid pressure in intermediate pressure region 91 exerted on valve member 103 on an effective area thereof, which cifective area includes the net area 114 of piston member 95 and a central portion of bulkhead 87. It will be understood more fully in the hereinafter described operation of valve assembly 11 that outlet chamber 57 is a low pressure region with the pressure therein being substantially lower than in intermediate pressure region 91, so that in effect the two opposing forces are provided by (1) spring 105 and (2) a net pressure times said effective area, which net pressure is equal to the pressure in intermediate pressure region 91 minus the pressure in outlet chamber 57. Also, it should be noted that since the fluid pressure in inlet chamber 53 is not introduced at the end of the piston member 71 but only on the exposed portion of side wall 75 that there is no necessity for a passageway to convey fluid pressure to an opposing area for balancing the pressure on the end of the piston member, as was necessary in my said Patent No. 2,785,660, thus a1- lowing a simpler and improved structure in the present invention.

Valve member 103 will remain in the closed position shown in FIG. 2, as long as a controlled throttling valve 115 remains closed, which controlled valve determines the discharge of fluid from intermediate chamber 55 and which controlled valve will be explained hereinafter in more detail. The aforementioned fact that valve member 103 will remain in the closed position is so for the following reasons:

The fluid pressure in jack cylinder 17 is communicated to intermediate pressure region 91 by leakage between piston 71 and opening 69 and between the piston and cylinder 74. There is no escape for fluid from intermediate pressure region 91 because valve 115 is closed and piston member 95 is seated fluid-tight so that full pressure is exerted on the aforementioned eifective area of valve member 3. When said full pressure is exerted on said elfective area, said net pressure is greater than the force of spring 105 and valve member 103 will remain in said closed position. The spring tension of spring 105 should be so chosen that it exerts at all times a smaller force than that due to the pressure in inlet chamber 53 due to an unloaded elevator car.

Controlled throttling valve 115 and its associated parts are preferably constructed similar to the lowering valve of my Patent No. 2,355,164, previously referred to. The following general description of valve 115 will suflice since a more detailed description may be obtained by referring to said Patent No. 2,355,164. Valve 115 includes a throttling valve member 116 co-operating with a discharge port 117, provided in second partition 51. Valve member 116 includes a disc 118 and wings 119 extending from the disc, and which wings have shaped notches 120 therebetween. Disc 1118 is provided with a beveled seat 121 fitted fluid tight to a corresponding seat at the end of discharge port 117. Wings 119 fit closely in discharge port 117 and notches 120 provide fluid passageways when valve member 116 moves to the right, as viewed in FIG. 2. A piston 122, which is concentric with valve member 116 and substantially greater in cross-sectional area than discharge port 117, is rigidly connected to disc 118 by a stem 123, and is slidably mounted in a cylinder 124 provided in valve body 47. Cylinder 124 extends through the wall of the valve body 47 where it is closed off by a cover 125 mounted on the valve body as by bolts 126. The right hand edge of piston 122 is formed helically, and is also notched to receive a transverse bar 135, the center of which engages a slot 137 in adjusting screw 139 that is threaded into cover 125. A handle 141 is fixedly mounted on the end of screw 139 so that by turning the handle adjusting screw 139 is turned to rotate piston 122. A Spring 143 biases piston 122 to the left or closed position, as viewed in FIG. 2, and keeps bar 135 in slot 137. A passage 145 is communicated at one end to the interior of cylinder 124 through a hole in the wall of the cylinder, which hole is so positioned that it will be covered or cut-off by piston 122 after a partial rightward motion thereof. Thus, the cut-off point of passage 145 may be adjusted by rotating piston 122, as above described to cause the helical edge of the piston to cut off the passage at varying points in the travel of the piston.

The chamber 146 established by cylinder 124 by piston 122 is connected to intermediate pressure region 91 by a conduit 147, an adjustable restriction valve 149, and a conduit 153. Chamber 146 may also be put in communication with out-let chamber 57 through an adjustable restriction valve 155, a magnetic valve .159, and a conduit 161. Another path is provided from chamber 146 to outlet chamber 57 through passage 145, a magnetic valve 163 and conduit 161. Valves 149 and 155 respectively include screw needles 164 and 165 for varying the restrictions of the valves.

When magnetic vaves 159 and 163 are de-energized, their needles 166, 167 close fluid tight and there is no path of escape for fluid from chamber 146 to outlet chamber 57. Thus, piston 122 and valve member 116 are held firmly in the closed position, both by the bias of spring 143 and by the fluid pressure existing in. intermediate pressure region 91 which is communicated to chamber 146 through the path above described. Since piston member 71 cannot entirely close off leakage into intermediate pressure region 91 and with no egress available, the pressure in the intermediate pressure region will equal that in inlet chamber 53. Since the full pressure is also exerted on valve member 103, holding piston on its seat, as heretofore explained, leakage is, therefore, prevented at all points in valve assembly 11.

To lower elevator car 18, magnetic valve 159 is energized by suitable switches and electrical circuits not shown. This will cause the pressure in chamber 146 to be reduced since fluid escapes from the chamber through conduit 16 1 into the low pressure region in outlet chamber 57 at a greater rate than fluid enters chamber 146 through conduit 153. This is due to the fact that needle 165 is adjusted to provide about twice the opening afforded by needle 164. As a result, the pressure in intermediate pressure region 91 acting to the right on piston 122, as viewed in FIG. 2, is greater than the sum of the pressures acting to the left on the opposite side of the piston. Piston 122, therefore, moves to the right to open valve 115 and permit fluid to discharge through port 117. This causes the pressure in intermediate pressure region 91 to drop, which pressure will fall until unable to oppose the bias of spring 105, whereupon valve member 103 will move to the right, as viewed in FIG. 2, gradually moving notches 79 into inlet chamber 53, thereby admitting corresponding fluid flow to the intermediate pressure region 91. When the pressure in intermediate pressure region 91 is such as to balance the bias of spring 105, valve member 103 will stop moving. A valve 115 opens wider and wider, increasing the flow from intermediate pressure region 91, to outlet chamber 57, the pressure in intermediate pressure region 91 will tend to remain slightly less than enough to balance spring which will cause valve member 103 to follow the movement of valve and open throttling valve 80 progressively wider. The opening of valve 115 will be limited by abutment of piston 122 against screw 139. When the valve 115 reaches its limit of opening, as above described, the tendency for pressure to drop in intermediate pressure region 91 ceases and valve member 103 likewise ceases to move.

It will be understood that with a given opening of valve 115, as for example, the fully open position above described, the pressure in intermediate pressure region 91 will remain substantially constant regardless of the pressure variation in inlet chamber 53. Thus, with a heavier load in elevator car 18, which produces a greater pressure in inlet chamber 53, valve member 103 willmove to the left as viewed in FIG. 2, to throttle down the fluid flow so that the pressure will remain the same in intermediate pressure region 91; and with a lighter load, valve member 103 will move to the right, as viewed in this figure, to increase the fluid flow and likewise keep the fluid pressure in intermediate pressure region 91 constant. Since, with any given opening of valve 115, the pressure in intermediate pressure region 91 remains substantially constant, the volumetric flow through valve assembly 11 will remain substantially constant and therefore cause a substantially constant lowering speed of car 18 with any given opening of valve 115.

Thus, from the foregoing, it will be understood that for any given flow or setting of valve 115, when the load in elevator car 18 increases and valve member 103 moves to the left, as above described, spring 105 will be moved towards more compression and when the load in elevator car 18 decreases and valve member 103 moves to the right, spring 105 will be allowed to expand. As is a common characteristic of ordinary springs, spring 105 will vary in force exerted as it is compressed or allowed to expand. Thus, as spring 105 is compressed by valve member 103, the force exerted by the spring increases somewhat; and as spring 105 expands, the force exerted by the spring decreases somewhat. This is an undesirable condition, since it will cause somewhat of a variation in the pressure in intermediate pressure region 91. In my Patent No. 2,785,660, heretofore referred to, an attempt was made to reduce this undesirable effect by providing a relatively long spring having a small amount of force change as the over-all length of the spring changed during compression and expansion. It has been found that this undesirable effect can be overcome by the use of the compensating device of the present invention, which device comprises a projection from stem 93, preferably in the form of a disc 169 integrally formed on the stem intermediate the ends thereof and disposed in the path of fluid flow through throttling valve 80. The principle of operation of said compensating device is as follows:

For a given flow-rate, the impact is greater when high pressure fluid passes through a small opening than when the same quantity of low pressure fluid passes through a larger opening. Thus, when the opening of throttling valve 80 is small as occurs with a high pressure in inlet chamber 53, as heretofore described, the impact on disc 169 will be greater which will compensate for the greater force exerted by spring 105, and when the opening of throttling valve 80 is greater which occurs with a lower fluid pressure in inlet chamber 53, less force is exerted by the fluid on disc 169, which is offset by the smaller force exerted by spring 105. The exactness of this compensation may be regulated by varying the diameter of disc 169 progressively until best action is obtained. Thus, with the use of this novel compensating device, a better regulation can be obtained over that shown in my said Patent No. 2,785,660 and a smaller, less bulky spring can be used.

When elevator car 18, in its lowering motion, approaches a landing at which stopping is desired, electrical circuits, not shown, are switched, as by switches, not shown, located in the hoist way and engaged by elevator car 18, to de-energize magnetic valve 159 and simultaneously energize magnetic valve 163. Since the orifice of passage 145 into cylinder 124 is, at this time, covered by piston 122, there will be no escape for fluid from chamber 146, so pressure therein rises nearly to equal that in intermediate pressure region 91 and piston 122, with valve member 116 moves to the left, as viewed in FIG. 2, at a rate determined by the setting of needle 164. As valve 115 closes and restricts the flow through discharge port 117, the pressure in intermediate pressure region 91 tends to rise, and this rise applied to valve 0 member 103 causes it to move to the left, as viewed in FIG. 2, restricting the fluid flow through opening 69 and restricting the pressure rise in intermediate pressure region 91. Since the fluid passages involved in the motion of valve member 103 are relatively unrestricted, this valve member follows very closely any change in pressure in intermediate pressure region 91 with no perceptible time lag as compared with the slower motion of valve member 116.

When piston 122 travels far enough to the left to uncover passage 145, egress is afforded for fluid entering cylinder 124 through conduit 153, and closing motion of valve member 116 is interrupted. The elevator will now be descending at leveling speed, typically about onefifth of normal lowering speed. Notches 79 will, therefore, have been closed nearly four-fifths, but not quite in proportion because the additional compression of spring 105 adds somewhat to the force exerted thereby. Thus, the pressure in intermediate pressure region 91 will be somewhat higher than when full speed lowering was in progress as heretofore described, but handle 141 may be turned to change the position of piston 122, which, in turn, will give the desired leveling speed.

This leveling speed, for the same reasons heretofore described, for the faster lowering speed, will remain constant regardless of load changes, since with a heavier load, throttling valve 80 will move towards closure to restrict the necessary fluid to maintain pressure in intermediate pressure region 91 constant, and since the slightly greater tension of spring will be overcome by the greater impact of the fluid stream against disc 169.

It is to be noted from a comparison of the above description of the conditions existing in valve assembly 11 when the leveling speed is produced and when the higher lowering speed is produced, that the valve assembly 11 does not strictly regulate pressure to a fixed value, but only to a value varying slightly with flow and hardly at all with fluid pressure in inlet chamber 53.

The next step in the operation after the leveling speed is maintained, occurs when magnetic valve 163 is de-energized, which causes the pressure in cylinder 124 to build up and the valve to close which, in turn, causes throttling valve 80 to close, and consequently all flow of fluid through valve assembly 11 is stopped, which stops the elevator car 18. As long as controlled valve 115 remains closed, car 18 will remain completely stationary since there is no escape of fluid from intermediate pressure region 91, as heretofore described, and consequently there is absolutely no fluid flow through valve assembly 11.

From the foregoing description, it is apparent that the valve assembly 11 of the present invention provides means for maintaining different lowering speeds constant at selected predetermined values which depend upon the opening of controlled valve 115, and which lowering speeds remain constant regardless of load variations whereby closing time of the valve assembly and, therefore, distance traveled during such time are, likewise, independent of load.

Although the invention has been described and illustrated with respect to a preferred embodiment thereof, it is to be understood that it is not to be so limited since changes in modification may be made therein which are within the full intended scope of this invention as hereinafter claimed.

I claim:

1. In a hydraulic elevator control system of the type provided with a fluid inlet chamber connected to a source of fluid under pressure, means providing an intermediate chamber, means providing a cylindrical opening communicating said inlet chamber with said intermediate chamber, a throttling member slidably mounted in said opening and movable to various positions to control the flow through the opening and into said intermediate chamber, said throttling member being exposed to said inlet chamber adjacent the side walls only of said throttling member whereby the pressure in said inlet chamber does not directly influence the position of said throttling member, controlled valve means communicating with said intermediate chamber and operable to various degrees of opening for controlling the discharge of fluid from said intermediate chamber, positioning means associated with said throttling member and sensitive to fluid pressure in said intermediate chamber to adjust the throttling eifect of said throttling member so that the fluid pressure in said intermediate chamber is substantially constant for any selected opening of said controlled valve means.

2. The structure according to claim 1 in which said positioning means comprises means providing a cylinder communicating adjacent one end thereof with said intermediate chamber, piston means in said cylinder having an effective area exposed to the fluid pressure in said intermediate chamber, means providing a low pressure region lower in pressure than the pressure in said intermediate chamber and communicated with said cylinder adjacent the end opposite from the end communicating with said intermediate chamber whereby said piston means is adapted to be urged by the fluid pressure in said intermediate chamber towards said low pressure region, said piston means being connected to said throttling member and being arranged so that movement of said piston means towards said low pressure region is eflective to move said throttling member towards closure of said opening, and spring means biasing said piston means in a direction opposite from said fluid pressure acting against said piston means and arranged so that the fluid pressure in said intermediate chamber is substantially constant for any selected degree of opening of said controlled valve means.

3. In a hydraulic fluid system having a source of hydraulic fluid under pressure, a valve assembly comprising means providing a fluid inlet chamber and an intermediate chamber, means providing a cylindrical opening communicating said inlet chamber with said intermediate chamber, conduit means communicating said source of fluid with said inlet chamber whereby said inlet chamber is adapted to receive hydraulic fluid under pressure from said source, a first throttling member slidably mounted in said opening and movable to various positions to control the flow through said opening and into said intermediate chamber, said first throttling member being exposed to said inlet chamber adjacent the side Walls only of said first throttling member whereby the pressure in said inlet chamber does not directly influence the position of said first throttling member, means providing a discharge port for said intermediate chamber, controlled valve means including a second throttling member slidably mounted in said discharge port and movable to various selected positions in said port to vary the eifective size of the opening of said discharge port, positioning means associated with said first throttling member and sensitive to fluid pressure in said intermediate chamber to adjust the throttling effect of said first throttling member so that the fluid pressure in said intermediate chamber is substantially constant for any selected position of said second throttling member whereby the volumetric fluid flow rate through said valve assembly is substantially constant at any selected position of said second throttling member.

4. The structure according to claim 3 in which said positioning means comprises means providing a cylinder communicating adjacent one end thereof with said intermediate chamber, piston means in said cylinder and having an effective area exposed to the fluid pressure in said intermediate chamber, means providing a low pressure region lower in pressure than the pressure in said intermediate chamber and communicated with said cylinder adjacent the end opposite from the end communicating with said intermediate chamber whereby said piston means is adapted to be urged by the fluid pressure in said intermediate chamber towards said low pressure region, said piston means being connected to said first throttling member and being arranged so that movement of said piston means towards said low pressure region is efiective to move said first throttling member towards closure of said opening, and spring means biasing said piston means in a direction opposite from said fluid pressure acting against said piston means and arranged so that the fluid pressure in said intermediate chamber is substantially constant for any selected position of said second throttling member.

5. The structure according to claim 4 in which said positioning means includes a projection disposed in the stream of hydraulic fluid flow from said opening into said intermediate chamber and arranged so that the increasing tension of said spring means acting on said piston means as it is moved in a direction to carry said first throttling member towards closure of said opening is compensated for by the increasing opposite force ofthe stream of hydraulic fluid impinging on said projection.

6. In a hydraulic fluid system having a source of hydraulic fluid under pressure, a valve assembly comprising a valve body, a valve member slidably mounted in said valve body; said valve member including a first throttling member including a cylindrical side wall provided with notches adjacent one end thereof, a piston member smaller in diameter than said first throttling member and a stem interconnecting said first throttling member and said piston member so that said first throttling member and said piston member move together; means forming a fluid inlet chamber in said valve body, conduit means communicating said source of fluid with said inlet chamber whereby said inlet chamber is adapted to receive hydraulic fluid under pressure from said source, said first throttling member being exposed to said inlet chamber adjacent the side walls only of said first throttling member whereby the pressure in said inlet chamber does not directly influence the position of said first throttling member, means forming an intermediate chamber in said valve body, means forming an opening between said inlet chamber and said intermediate chamber to permit flow of fluid from said inlet chamber to said intermediate chamber, said first throttling member being slidable in said opening and movable to various positions therein to control the fluid flow firom said inlet chamber to said intermediate chamber through said notches, said valve body being provided with a discharge port for said intermediate chamber to permit discharge of hydraulic fluid from said intermediate chamber, controlled valve means including a second throttling member cooperating with said discharge port for selectively varying the effective size of the discharge port opening, a cylinder in said valve body having one end communicating'with said intermediate chamber and having the other end communicating with a low pressure region, said piston member being slidably received in said cylinder, said valve member having an effective area exposed to the fluid pressure of said intermediate chamber and having an opposing area on said piston member exposed to said low pressure region so that said valve member is urged in a direction to carry said first throttling member towards closure of said opening under influence of the fluid pressure acting against said effective area, compression spring means biasing said valve member in a direction opposite from said pressure acting against said effective area and being arranged so that said valve member is sensitive to the fluid pressure in said intermediate chamber and moves to various positions depending upon the position of said second throttling member and so that with any given position of said second throttling member said first throttling member is moved in said opening to maintain the fluid pressure in said intermediate chamber substantially constant regardless of the fluid pressure in said inlet chamber whereby the volumetric fluid flow through said valve assembly is substantially constant at any selected position of said second throttling member.

7. In a hydraulic fluid system having a source of hy draulic fluid under pressure, a valve assembly comprising a hollow valve body including first and second partitions provided in the interior thereof to establish an inlet chain ber, an intermediate chamber, and an outlet chamber; sa d first partition separating said inlet chamber and said mtermediate chamber, said second partition separatmg said intermediate chamber and said outlet chamber, conduit means communicating said source of fluid with said inlet chamber whereby said inlet chamber is adapted to receive hydraulic fluid under pressure from said source, said first partition being provided with an opening there through adapted to permit flow of hydraulic fluid froiii said inlet chamber to said intermediate chamber, said valve body being provided with a discharge port for said intermediate chamber, controlled valve means cooperating with said discharge port for selectively varying the effective size of the opening of said discharge port, said valve body being provided with a first cylinder spaced from and in alignment with said opening through said first partition, means establishing a head chamber in communication with one end of said first cylinder, said first cylinder being in communication adjacent the opposite end from said head chamber with said inlet chamber, a hollow openended throttling member including a cylindrical side wall slidably received adjacent one end thereof in said first cylinder and slidably received adjacent the opposite end thereof in said opening in said first partition with the side wall only of said throttling member being exposed to said inlet chamber whereby the pressure in said inlet chamber does not influence the position of said throttling member, said side wall of said throttling member being provided with notches in the end thereof adjacent said opening in said first partition, said throttling member being movable to various positions in said opening in said first partition to control the fluid flow from said inlet chamber through said notches into said intermediate chamber, said throttling me'mberbeing provided with a transverse bulkhead interiorly thereof, said bulkhead being provided with apertures therethrough to allow free flow of fluid from opposite sides of said bulkhead whereby the pressure of fluid is substantially the same in an enclosed intermediate pressure region defined by said head chamber, the portion of said first cylinder exposed by said throttling member, the interior of said throttling member and said intermediate chamber; positioning means including a piston member establishing with said throttling member a unitary valve member, said valve member having an effective area exposed to the fluid pressure of said intermediate region and having an opposing area exposed to a low pressure region in said outlet chamber so that said valve member is urged in a direction towards closure of said opening in said first partition under influence of the fluid pressure force acting against said effective area, compression spring means biasing said valve member in a direction opposite from said force acting against said efiective area so that said valve member is sensitive to the fluid pressure in said intermediate pressure region and movable to various positions depending upon the effective size of said discharge port and so that with any given efiective size of said discharge port said throttling member is moved in said opening in said first partition to maintain the fluid pressure in said intermediate chamber substantially constant regardless of the fluid pressure in said inlet chamber whereby the volumetric fluid flow rate through said valve assembly is substantially constant for any given effective size of said discharge port.

8. A valve assembly for receiving fluid flow at a variable pressure and regulating the flow to a predetermined volumetric rate regardless of the pressure of the fluid received, said valve assembly comprising a valve body, a valve member slidably mounted in said valve body; said valve member including a first throttling member including a cylindrical sidewall provided with notches adjacent one end thereof, means forming a fluid inlet chamber in said valve body, said first throttling member .being exposed to said inlet chamber adjacent the side walls only of said first throttling member whereby the fluid pressure in said inlet chamber does not influence the position of said first throttling member, means forming an intermediate chamber in said valve body, a partition separating said inlet chamber and said intermediate chamber, said partition being provided with an opening therethrough adapted to permit flow of fluid from said inlet chamber to said intermediate chamber, said first throttling member being slidable in said opening and movable to various positions therein to control the rate of fluid flow from said inlet chamber to said intermediate chamber through said notches, said valve body being provided with a discharge port for said intermediate chamber to permit discharge of hydraulic fluid from said intermediate chamber, controlled valve means including a second throttling member cooperating with said discharge port for selectively varying the effective size of the discharge port opening, said valve member having an effective area exposed to the fluid pressure of said intermediate chamber and having an opposing area exposed to a low pressure region so that said valve member is urged in a direction to carry said first throttling member towards closure of said opening under influence of the fluid pressure force acting against said eitective area, compression spring means biasing said valve member in a direction opposite from said force acting against said effective area and so that said valve member is sensitive to the fluid pressure in said intermediate chamber and moves to various positions depending upon the position of said second throttling member and so that with any given position of said second throttling member said first throttling member is moved in said opening to maintain the fluid pressure in said intermediate chamber substantially constant regardless of the fluid pressure in said inlet chamber whereby the volumetric fluid flow through said valve assembly is substantially constant at any selected position of said second throttling member.

9. In a hydraulic fluid system having a source of hydraulic fluid under pressure, a valve body providing an inlet chamber and an intermediate chamber, conduit means communicating said source of fluid with said inlet chamber whereby said inlet chamber is adapted to receive hydraulic fluid under pressure from said source, means providing a cylindrical opening communicating said intermediate chamber with said inlet chamber and adapted to permit flow of hydraulic fluid from said inlet chamber to said intermediate chamber, controlled throttling valve means communicating with said intermediate chamber and operable to various throttling positions for controlling the discharge of fluid from said intermediate chamber, said valve body being provided with a first cylinder spaced from and in alignment with said opening and being provided with a second cylinder concentric with said first cylinder, means establishing a head chamber in communication with one end of said first cylinder, said first cylinder being in communication adjacent the opposite end from said head chamber with said inlet chamber, a throttling member including a cylindrical side wall slidably received adjacent one end thereof in said first cylinder and slidably received adjacent the opposite end thereof in said opening with the side wall only of said throttling member being exposed to said inlet chamber whereby the pressure in said inlet chamber does not influence the posi tion of said throttling member, said side wall of said throttling member being provided with notches in the end thereof adjacent said opening, said throttling member being movable to various positions in said opening to control the fluid flow from said inlet chamber through said notches into said intermediate chamber, means communicating said head chamber and said intermediate chamber to permit free flow of fluid therebetween, a piston member slidably received in said second cylinder, said second cylinder being provided with a seat and said piston member being provided with a seating portion adapted to cooperate with said seat to substantially completely close off any fluid leakage through said second cylinder when said piston member is in a seated position, a stem connected at one end to said bulkhead and projecting axially away from said throttling member towards said piston member and connected thereto whereby said throttling member and said piston member are interconnected to establish a unitary valve member, said valve member having an efiective area exposed to the fluid pressure of said intermediate region and having an opposing area on said piston member exposed to a low pressure region so that said valve member is urged in a direction towards closure of said opening and towards seating of said piston member under influence of the fluid pressure force acting against said effective area, compression spring means biasing said valve member in a direction opposite from said force acting against said effective area, so that said valve member is sensitive to the fluid pressure in said intermediate pressure region and movable to various positions depending upon the position of said controlled throttling valve means and so that with any given position of said controlled throttling valve means said throttling member moves in said opening to maintain the fluid pressure in said intermediate chamber substantially constant regardless of the fluid pressure in said inlet chamber whereby the fluid flow through said controlled throttling valve means is substantially constant at any selected position of said controlled throttling valve means.

10. In a fluid system having a first chamber adapted to receive fluid under pressure and a second chamber communicated with said first chamber through an opening and said second chamber having a discharge port, the improvement in control means for maintaining the fluid pressure in said second chamber constant with a given effective size of said discharge port, said control means comprising means providing a first cylinder spaced from and in alignment with said opening, means providing a second cylinder concentric with said first cylinder, means establishing a head chamber in communication with one end of said first cylinder, said first cylinder being in communication adjacent the opposite end from said head chamber with said first chamber, a throttling member including a cylindrical side wall slidably received adjacent one end thereof in said first cylinder and slidably received adjacent the opposite end thereof in said opening with the side wall only of said throttling member being exposed to said first chamber whereby the pressure in said first chamber does not directly influence the position of said throttling member, said side Wall of said throttling member being provided with notches in the end thereof adjacent said opening, said throttling member being movable to various positions in said opening to control the fluid flow from said first chamber through said notches to said second chamber, means communicating said head chamber and said second chamber to permit free flow of fluid therebetween, a piston member slidably received in said second cylinder, means interconnecting said throttling member and said piston member to establish a unitary valve member, said valve member having an effective area exposed to fluid pressure of said intermediate region and having an opposing area on said piston member exposed to a low pressure region so that said valve member is urged in a direction towards closure of said opening under influence of the fluid pressure force acting against said effective area, compression spring means biasing said valve member in a direction opposite from said force acting against said effective area so that said throttling member is moved in said opening to maintain the fluid pressure in said second chamber substantially constant regardless of the fluid pressure in said first chamber.

11. The structure according to claim 10 which includes a projection fixedly mounted on said valve member and disposed in the stream of fluid flow through said opening into said second chamber and arranged so that the increasing tension of said spring means acting on said valve member as it is moved in a direction to carry said throttling member towards closure of said opening is compensated for by the increasing opposite force of the stream of fluid impinging on said projection.

12. In a fluid system having a first chamber adapted to receive fluid under pressure and a second chamber communicated with said first chamber through an opening and said second chamber having a discharge port, the improvement in control means for maintaining the fluid pressure in said second chamber constant with a given effective size of said discharge port, said control means comprising a throttling member slidably mounted in said opening and movable to various positions to control the flow through the opening and into said second chamber, said throttling member being exposed to said first chamber adjacent the side walls only of said throttling member whereby the pressure in said first chamber does not directly influence the position of said throttling member, positioning means associated with said throttling member; said positioning means including an effective area thereof exposed to the pressure in said second chamber for biasing said throttle member in a closing direction, spring means for biasing said throttling member in an opening direction against the force acting against said effective area so that said throttling member is moved in said opening to maintain the fluid pressure in said second chamber substantially constant regardless of the fluid pressure in said first chamber, and projection means disposed in the stream of fluid flow from said opening into said second chamber and arranged so that the increasing tension of said spring means acting on said throttling member as it is moved in a direction to carry said throttling member towards closure of said opening is compensated for by the increasing opposite force of the stream of hydraulic fluid impinging on said projection means.

13. In a fluid system having a first chamber adapted to receive fluid under pressure and a second chamber communicated with said first chamber through an opening and said second chamber having a discharge port, the improvement in control means for maintaining the fluid pressure in said second chamber constant with a given effective size of said discharge port, said control means comprising a throttling member slidably mounted in said opening and movable to various positions to control the flow through the opening and into said second chamber, said throttling member being exposed to said first chamber adjacent the side walls only of said throttling member whereby the pressure in said first chamber does not directly influence the position of said throttling member, positioning means associated with said throttling member; said positioning means including an effective area thereof exposed to the pressure in said second chamber for biasing said throttling member in a closing direction, spring means for biasing said throttling member in an opening direction against the force acting against said effective area so that said throttling member is moved in said opening to maintain the fluid pressure in said second chamber substantially constant regardless of the fluid pressure in said first chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,785,660 Jaseph Mar. 19, 1957 

